Preimmunization with a heat-killed preparation of Mycobacterium vaccae enhances fear extinction in the fear-potentiated startle paradigm
Abstract
The hygiene hypothesis or "Old Friends" hypothesis proposes that inflammatory diseases are increasing in modern urban societies, due in part to reduced exposure to microorganisms that drive immunoregulatory circuits, and a failure to terminate inappropriate inflammatory responses. Inappropriate inflammation is also emerging as a risk factor for trauma-related, anxiety, and affective disorders, including posttraumatic stress disorder (PTSD), which is characterized as persistent re-experiencing of the trauma after a traumatic experience. Traumatic experiences can lead to long-lasting fear memories and exaggerated fear potentiation of the acoustic startle reflex. The acoustic startle reflex is an ethologically relevant reflex and can be potentiated in both humans and rats through Pavlovian conditioning. Mycobacterium vaccae NCTC 11659 is a soil-derived bacterium with immunoregulatory and anti-inflammatory properties that has been demonstrated to confer stress resilience in mice. Here we immunized adult male Sprague Dawley rats 3×, once per week, with a heat-killed preparation of M. vaccae NCTC 11659 (0.1mg, s.c., in 100µl borate-buffered saline) or vehicle, and, then, 3weeks following the final immunization, tested them in the fear-potentiated startle paradigm; controls were maintained under home cage control conditions throughout the experiment (n=11-12 per group). Rats were tested on days 1 and 2 for baseline acoustic startle, received fear conditioning on days 3 and 4, and un…
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Heat-killed Mycobacterium vaccae accelerates extinction learning in adult rats.
“whereas heat-killed Mycobacterium vaccae has the opposite effect, accelerating extinction learning in adult rats (Fox et al., 2017).”
From The Microbiota-Gut-Brain Axis (2019) · cites this paper as Fox et al., 2017
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- Authors
- Fox, J. H., Hassell, J. E., Siebler, P. H., Arnold, M. R., Lamb, A. K., Smith, D. G., Day, H. E. W., Smith, T. M., Simmerman, E. M., Outzen, A. A., Holmes, K. S., Brazell, C. J., & Lowry, C. A.
- Affiliations
- University of Colorado Boulder (US)
- Corresponding author
- Lowry, Christopher A.
- ORCID
- Venue
- Brain, Behavior, and Immunity
- Publisher
- Elsevier BV
- Published
- 2017-11
- Volume
- 66
- Pages
- 70-84
- ISSN
- 0889-1591 (ISSN-L)
- OpenAlex
- W2751000579
- Cited by
- 44
- References
- 10
- Citations by year
- 2026: 2 · 2025: 2 · 2024: 1 · 2023: 4 · 2022: 4 · 2021: 3 · 2020: 7 · 2019: 11 · 2018: 7 · 2017: 3
- FWCI
- 4.40
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Brain Behavior and Immunity (publishedVersion)
- PubMed (publishedVersion)
- Funders
- Howard Hughes Medical Institute
- Topics
- Life Sciences › Neuroscience › Cognitive Neuroscience › Memory and Neural Mechanisms
- Life Sciences › Neuroscience › Behavioral Neuroscience › Stress Responses and Cortisol
- Social Sciences › Psychology › Clinical Psychology › Posttraumatic Stress Disorder Research
- Keywords
- Mycobacterium vaccae, fear extinction, fear-potentiated startle, acoustic startle response, serotonergic signaling, dorsal raphe nucleus, median raphe nucleus, tryptophan hydroxylase 2, 5-HT1A receptor, serotonin transporter, SLC22A3, post-traumatic stress disorder, hygiene hypothesis, immune regulation
- MeSH terms
- Organic Cation Transporter 3, Animals, Bacterial Vaccines, Brain, Conditioning, Classical, Extinction, Psychological, Fear, Immunization, Male, Mycobacterium, RNA, Messenger, Serotonin, Reflex, Startle, Stress, Psychological, Tryptophan Hydroxylase, Vaccines, Inactivated, Rats, Sprague-Dawley, Organic Cation Transport Proteins, Receptor, Serotonin, 5-HT1A, Serotonin Plasma Membrane Transport Proteins
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